Electrical apparatus and method of manufacturing and operating the same.



J. T. H. DEMPSTER. ELECTRICAL APPARATUS AND METHOD or MANUFAGTUBIN G AND OPERATING THE SAME.

AYPLIOATION FILED AUG. 23, 1904.

Patented Apr. 6, 1909.

Fig. I. I9 7 Fig. 2.

E: I. 2. E

Inventor John T. H. Dempster bg MM DItt'g.

Witnesses: MW

1 UNITED str-ATEsrA'rENr OFFICE."

JOHN T. H. DEMPSTER, OE SCHENECTADY, NEW YORK, ASSIGNORTO GENERAL ELECTRIC COMPANY, A GQRPORATION OF NEW YORK. V

ELECTRICAL APPARATUS METHOD OF MANUFACTURING AND OPERATING THE SAME.

Specification 0: Letters Patent.

Patented April 6, 1909.

Application filed August 28, 1804. Serial No. 221,884.

Schenectad county of Schenectady, State" of New Yor have invented certain new and useful Improvements in Electrical Ap aratus and Methods of Manufacturin and gperating the Same, of which the ollowing is a specification.

In the manufacture and operation of static electric condensers of the ordinary form composed of alternate layers of conducting material such as copper, tin-foil and the. like, and dielectric such as paraflin paper or the like, difliculty is frequently experienced from air in the form of bubbles located in the layers of dielectric or between the layers of conducting material and the layers of dielectric. If

such a condenser is immersed in a bath of a fluid dielectric material such as oil, melted paraffin or the like, and the bath is subjected to a suitable pressure, I have found that not only are the air bubbles reduced in size by the pressure to which they are exposed, but that the fluid dielectric appears to dissolve or take up the air under these circumstances. If the pressure on the fluid dielectric be reduced the air does not thereafter collect in comparatively large bubbles such as were origmally present. This is fparticularly true where the bath consists o paraffin or the like which .is allowed to solidify before the pressure is reduced. This result of itself ma-.

terially improves the condenser. I have found, however, if the pressure to which the bath is subjected is not reduced but on the contrary is maintained during the operation of the condenser, that excellent results are i obtained thereby. The advantages obtained appear to be due more or less to the fact that t e specific inductive capacity of the dielectric is increased and its resistance to puncture under the-stresses produced by the difference of. potential between the conducting plates, layers, or members of the con-.

denser, is also increased. In any event, the effect of maintaining the bath under pres.- sure during normal operation is to increase the ca acity of the condenser and to decrease 1ts liability to break down under operating conditions.

It Wlll be obvious to all those skilled in the art, that the, advantages to be obtained by maintaiping material such as oil or parafiin under ressure, are not limited to the case of con ensers but are useful in other relations, as for instance in connection with transformers of the ordinary ty e.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of my invention, however, reference may be had to the s wpanying drawings and description.

Of the drawings, Figure 1 is a sectional elevation of a static electric condenser and easing; Fig. 2 is an elevation of a portion of a condenser section which may be employed in Fig. 1; and Fig. 3 is a sectional elevation showing a transformer and casing.

Referring particularly to Figs. 1 and 2, 1 represents the body of the inclosing metal casing. 2 represents the condenser proper located in the casing. The condenser 2 is shown as made u of a number of sections 3, each of which is formed of a number of conducting plates 4 of one polarity alternating with a number of conductingplates 5 of a different polarity. The conducting plates 4 and 5 may be formed of any suitable material such as tin-foil, sheet copper, or the like, and adjacent plates 4 and 5 are separated by layers 6 of insulating material. The insulating materialG may be 1n the form of a number of sheets of aper or the like which may be impregnated with oil or paraffin. Heavy layers or sheets 7 of insulating material are employed to separate the condenser sections 3 from each other and from end members 8. The end members 8 and connecting bolts 9 form a frame in which the condenser sections are clamped. The end members 8 rest on blocks or posts of wood 10, which in turn rest upon the bottom of the casing 1.

The terminals 11 and 12 of the condenser pass through apertures formed for the urpose in the side wall of the casing 1, an are suitably insulated therefrom by bushings 13. Preferably the bushings 13 are formed of some material such as a glass having substantially the same coefiicient of expansion as the casing, which can practically be welded or cast into the openings in the casing, to form airand oil-tight joints'of great mechanical strength. The upper end of the casing is close by a plate or head 14 which is secured to the body of the casing by bolts 15 passin through a flange 16 formed at the u er en of the casing body 1. Any suitable means may be employed for making a strong oil-tight 'oint between the head 14 and the body 0 the casing A lp1pe 17 1s tapped into end late 14. sum ar plpe 18 is tapped into t e lower end of the casing. Valves 19 located adjacent to the casing are employed to open and close the pipes 17 and 18 as may be desired.

After the condenser 2 is placed in the easing and the connections are made to the terminals 11 and 12, the end member 14 s clamped tight] in place. The pipe 17 s then connected to an air-pum and air is exhausted from the interior 0 the casmg. After this, fluid insulating material is introduced into the casing through the pipe 18. The insulating material introduced at this time is not suflicient in amount to entirely fill the casing, but is suflicient to more than cover the condenser. The insulating material which is introduced may be in the form of a ermanent oil or may be paraflin or the like Treated to render it fluid. After the fluid insulating material is admitted in the manner described, the operation of the airpump and pipe 17 is continued for some time, and the insulating material if such that it solidifies when cold is maintained fluid by heatingthe casing. The result of this 0 eration is to cause the condenser to be t oroughly permeated by the fluid insulating materla As the fluid dielectric creeps into the condenser by what is substantially a capillary action, most of the air in the condenser is displaced. The air displaced is of course removed through the pipe 17. When this operation has been continued for the proper time (usually for several hours) the casin is entirel filled with insulating materia through t e ipe 18. After this occurs, the valve 19 in tlie pipe 17 is closed. Means are then em loyed to force the fluid dielectric material mto the casing until a fluid pressure in the casing is obtained amounting to several hundred pounds per s uare inch. After this pressure is attained, t e valve 19 may either be closed, or the pipe 18 may be left in communication with some ressureproduc' means. In any event, t e valve 19 shoul not'be closed when the insulating material introduced in it solidifies at ordinary'temperature, until after the solidification has taken place. The resiliency of the end member 14 and the casing member 1 may be relied upon to account for the slight difference in volume of the insulating material produced by ordinary temperature change. 1

Putting insulating material such as oil or paraflin under a pressure of several hundred pounds not only mechanically compresses any small bubbles of air which may have remained in the condenser after the original 0 eration, but as I have discovered causes t e fluid dielectric to dissolve or take up more or less air somewhat as water takes up carbonic acid gas under pressure.

Some of the advantages of my invention are attained therefore if the fluid ressure of the dielectric is maintained on y for a short time, as maintaining the fluid pressure even for a short time practically destroys all large air bubbles which ma have remained in the condenser. If a hig pressure is not to be permanently maintained, I find it advantageous to slightly reduce the amount of insulating material in the condenser casing and to again start the air pump, exhausting from the upper end of the casing after the amount of the insulating material in the casing has been reduced. After the air pump has been 0 erated for a short time, I again entirely fill t e casing with insulating material and then close both valves 19. Preferably, however, I maintain the insulating material within the casing under a pressure which may be in the neighborhood of several hundred pounds per square inch.

tions will allow. The effect of maintainingthe dielectric material under high pressure is to increase its specific inductive ca acity and to increase its ability to resist reakdown or puncturing stresses.

In Fig. 3 I have shown a casin substantially similar to that shown in ig. 1, in which a transformer 20 com rising a core 21 and coils 22, is located. he terminals 23 of the transformer are let through the walls of the casing as are the terminals of the condenser shown in Fig. 1. I find it advantageous to fill the casi rounds the transformer wit insulating material such as oil, and to maintain this insulating material under a pressure of several hundred ounds while the transformer is operated. T e principal apparent advantage in this. case for maintaining the high pressure of the insulating material appears to be due to the increased stren th of the insulating material obtained there y. This is of course particularly important in connection with transformers in which comparatively high potentials are em 10 ed.

It will be read1ly understood by afit ose skilled in the art that many variations may be made in the forms in which my invention may be embodied and the uses to which it may be put, and I do not wish the claims hereinafter made to be limited to the specific embodiment. of my invention disclose more than is made necessary by the state of the art.

What I claim as new and'desireto secure by Letters Patent of the United States, is;

- 1. The method of removing air from a conwhich surunder a pressure denser which consists in immersing a condenser in a bath of liquid insulating material, and maintaining the insulating material under-such pressure during the normal operation of the condenser that air contained in said condenser is dissolved or taken up by the insulating material.

2. The method of removing air from electric apparatus which consists in immersing, anelectric apparatus in a bath of liquid insulating material, and maintaining said bath suflicient to cause air contained in said apparatus to be dissolved or taken up by the bath during the normal operation of the apparatus.

3. The method of removing air from electric apparatus, which consists inimmersing the apparatus in a bath of fluid insulating material, putting the insulating material under pressure suflicient to cause air in said 8?)? aratus to be dissolved or taken up by t 1e insulating material, and then reducing the ressure on said insulating material to a point below atmospheric pressure.

4. The method of removing air from, electric" apparatus \xhich consists in immersing the apparatus in a bathv of liquid material, putting the insulating material under a pressure sufficient to cause air in said apparatus to be dissolved in or taken up by the insulatparatus.

r it under said pressure during su ating material ingf material, reducing the pressure of the into a point below atmospheric pressure, thereafter raising the pressure of the insulatin material above atmospheric pressure, an maintaining it at that point during the normal operation of the ap- 5; The method of removing air from electric apparatus which consists in immersing electric apparatus in a bath of fluid insulating material, puttin the insulating material under a pressure su' cient to cause the air in said apparatus to dissolve in or be taken up by the insulating material, thereafter reducing the pressure on said insulatin material, and thereafter putting the insu ating material again under pressure and maintaining eration of the apparatus.

' 6. In a condenser, the combination with the conducting plates of a liquid dielectric material, under such 'gh pressure as to render air soluble therein.

In v. itness whereof, I have hereunto set my hand this 22nd day of August, 1904.

JOHN T. n. DEMPS TER.

Witnesses:

BENJAMIN B. HULL,

HELEN Onronn.

the normal op- 

